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Smtps

The document contains code for an SMTP server program that implements the basic SMTP protocol. The program creates a UDP socket, binds it to a port, and then exchanges messages with a client using functions like recvfrom(), sendto() to implement the SMTP commands HELO, MAIL FROM, RCPT TO, DATA, and QUIT.

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SHIFANA A
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31 views3 pages

Smtps

The document contains code for an SMTP server program that implements the basic SMTP protocol. The program creates a UDP socket, binds it to a port, and then exchanges messages with a client using functions like recvfrom(), sendto() to implement the SMTP commands HELO, MAIL FROM, RCPT TO, DATA, and QUIT.

Uploaded by

SHIFANA A
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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/*

NAME:SNEHA JOSEPH
ROLL NUMBER:31
PROGRAM NAME:SMTP SERVER
DATE:07.11.2016
*/
#include<stdio.h>
#include<string.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<stdlib.h>
#include<sys/types.h>
#include<netinet/in.h>
#define BUF_SIZE 256
int main(int argc,char* argv[])
{
struct sockaddr_in server,client;
char str[50],msg[20];
if(argc!=2)
printf("Input format not correct");
int sockfd=socket(AF_INET,SOCK_DGRAM,0);
if(sockfd==-1)
printf("Error in socket();");
server.sin_family=AF_INET;
server.sin_addr.s_addr=INADDR_ANY;
server.sin_port=htons(atoi(argv[1]));
client.sin_family=AF_INET;
client.sin_addr.s_addr=INADDR_ANY;
client.sin_port=htons(atoi(argv[1]));
if(bind(sockfd,(struct sockaddr *)&server,sizeof(server))<0)
printf("Error in bind()! \n");
socklen_t client_len=sizeof(client);
printf("server waiting......");
sleep(3);
if(recvfrom(sockfd,str,100,0,(struct sockaddr
*)&client,&client_len)<0)
printf("Error in recvfrom()!");
printf("\nGot message from client:%s",str);
printf("\nSending greeting message to client");
strcpy(str,"220 127.0.0.1");
sleep(10);
if(sendto(sockfd,str,sizeof(str),0,(struct sockaddr
*)&client,sizeof(client))<0)
printf("Error in send");
sleep(3);
if((recvfrom(sockfd,str,sizeof(str),0,(struct sockaddr
*)&client,&client_len)),0)
printf("Error in recv");
if(strncmp(str,"HELO",4))
printf("\n'HELO' expected from client....");
printf("\n%s",str);
printf("\nSending response...");
strcpy(str,"250 ok");
if(sendto(sockfd,str,sizeof(str),0,(struct sockaddr
*)&client,sizeof(client))<0)
printf("Error in send");
sleep(3);
if((recvfrom(sockfd,str,sizeof(str),0,(struct sockaddr
*)&client,&client_len))<0)
printf("Error in recv");
if(strncmp(str,"MAIL FROM",9))
printf("MAIL FROM expected from client...");
printf("\n%s",str);
printf("\nSending response....");
strcpy(str,"250 ok");
if(sendto(sockfd,str,sizeof(str),0,(struct sockaddr
*)&client,sizeof(client))<0)
printf("Error in send");
sleep(3);
if((recvfrom(sockfd,str,sizeof(str),0,(struct sockaddr
*)&client,&client_len))<0)
printf("Error in recv");
if(strncmp(str,"RCPT TO",7))
printf("\nRCPT TO expected from client....");
printf("\n%s",str);
printf("\nSending response....");
strcpy(str,"250 ok");
if(sendto(sockfd,str,sizeof(str),0,(struct sockaddr
*)&client,sizeof(client))<0)
printf("Error in send");
sleep(3);
if((recvfrom(sockfd,str,sizeof(str),0,(struct sockaddr
*)&client,&client_len))<0)
printf("Error in recv");
if(strncmp(str,"DATA",4))
printf("\nDATA expected from client....");
printf("\n%s",str);
printf("\nSending response....");
strcpy(str,"354 Go ahead");
if(sendto(sockfd,str,sizeof(str),0,(struct sockaddr
*)&client,sizeof(client))<0)
printf("Error in send");
if((recvfrom(sockfd,msg,sizeof(str),0,(struct sockaddr
*)&client,&client_len))<0)
printf("Error in recv");
printf("mail body received");
printf("\n%s",msg);
if((recvfrom(sockfd,str,sizeof(str),0,(struct sockaddr
*)&client,&client_len))<0)
printf("Error in recv");
if(strncmp(str,"QUIT",4))
printf("quit expected from client....");
printf("\nSending quit...");
strcpy(str,"221 OK");
if(sendto(sockfd,str,sizeof(str),0,(struct sockaddr
*)&client,sizeof(client))<0)
printf("Error in send");
close(sockfd);
return 0;
}

/*OUTPUT

s7csb-2@labb29:~/sneha31$ gcc smtps.c -o s


s7csb-2@labb29:~/sneha31$ ./s 2034
server waiting......
Got message from client:hi
Sending greeting message to client
HELO 127.0.0.1
Sending response...
MAIL FROMsneha@gmail.com
Sending response....
RCPT TOlmcst@gmail.com
Sending response....
DATA
Sending response....mail body received

welcome to lmcst

Sending quit...s7csb-2@labb29:~/sneha31$

*/

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